China News Service, July 7th. According to the official WeChat news of the Lunar Exploration and Aerospace Engineering Center, the Chang'e-4 mission "Yutu No. 2" lunar rover and lander were launched at 19:14 on July 5 and at 6:00 on July 6, respectively. Complete the hibernation settings, complete the 44th month day work, and enter the 44th month night sleep.

The total mileage of the lunar rover on the far side of the moon is 1239.88 meters.

Image source: Official WeChat of the Lunar Exploration and Aerospace Engineering Center

Chang'e-4 research results reveal the origin of the compositional anomaly in the Antarctic-Aiken Basin

  The South Pole-Aiken Basin is the largest impact basin on the Moon, with a diameter of over 2,400 kilometers.

The study of the South Pole-Aiken Basin is of great significance for revealing the origin of the lunar asymmetry, the impact process, the early evolution process and the composition of the deep material.

Orbital remote sensing observations show that there is a compositional anomaly in the center of the Antarctic-Aiken Basin. The planetary science team of Shandong University analyzed and interpreted the in-situ visible and near-infrared spectral data of the Yutu-2 lunar rover and found that the lunar crust is the Antarctic-Aiken composition anomaly. The main material source provides important constraints for the future exploration of materials in the Antarctic-Aiken Basin and even the deep parts of the moon.

  The main material components on the lunar surface are pyroxene and olivine, and the material composition at the bottom of the South Pole-Aiken Basin is abnormal.

Distribution of iron and pyroxene content inside and outside the Antarctic-Aiken Basin.

Image source: Official WeChat of the Lunar Exploration and Aerospace Engineering Center

  Most of the previous studies on the material composition of the Antarctic-Aiken Basin only focused on mafic minerals. Due to the anomalous characteristics of mafic in this region, there has even been a debate about whether the lunar mantle is peridotite or pyroxene.

Although according to the lunar magma ocean hypothesis, olivine and pyroxene are the main minerals of the lunar mantle, the plutonic magma intrusion after the formation of the lunar crust can also form rocks rich in olivine or pyroxene in the lunar crust, so olivine is enriched Or pyroxene is not evidence of origin from the lunar mantle.

So far, humans have not obtained samples from the Antarctic-Aiken Basin and returned to Earth, and their trace elements and isotopic characteristics cannot be known. Among the material composition information available through remote sensing or in situ detection, the plagioclase content also distinguishes crust-derived and mantle-derived rocks. key indicators.

  The plagioclase content in the material of the Antarctic-Aiken composition anomaly sputtered from the Finsen impact crater exceeds the plagioclase content that can be evolved during the impact melt differentiation process, so the formation of the mineralogy in the composition anomaly region has additional The addition of lunar shell material (Figure 2).

Numerical simulation studies believe that during the excavation process of the South Pole-Aiken impact, the lunar crust has been completely stripped, but in the subsequent reformation stage, the collapse of the instantaneous crater wall may cause the lunar crustal material to slip off the bottom of the basin.

In addition, other basin impact events after the Antarctic-Aiken impact event also produced a backfilling effect on the bottom of the Antarctic-Aiken Basin, and the exposed lunar mantle material or impact melting products during the formation of the basin are likely to have been diluted by the lunar crust material.

Mineralogical and geochemical unmixing analysis results show that the lunar soil on the surface of the anomalous area is composed of about 70% of the lunar crust material and about 30% of the material enriched in iron and incompatible elements.

Mineral composition and source reservoir of Chang'e-4 landing area.

Image source: Official WeChat of the Lunar Exploration and Aerospace Engineering Center